1. Field of the Invention
The present invention relates in general to locks for sliding doors and, more particularly, to a mortise lock for latching a door to a jamb using a pair of opposing hooks.
2. Description of the Prior Art
In order to improve the latch security, so-called multi-point latches have been developed and used, so that more than one latching element engage the striker plate attached to a jam to provide a more secure arrangement against forced entry.
Attempts have been made in the past to introduce a better mortise lock. U.S. Pat. No. 5,951,068, dated Sep. 14, 1999 and granted to Strong et al. for a xe2x80x9cLock for Sliding Doorxe2x80x9d, discloses a lock for a sliding closure. The lock includes a housing with a pair of hook shaped locking elements, the latter being mounted for rotation within the housing. A handle is coupled to a gear wheel that meshes with a pair of rack elements, located for sliding movement in the housing. A projection from each rack element engages in a curved slot of the locking element. Consequently, rotation of the handle results in a sliding movement of each of the racks, which causes the locking elements to move between a retracted first position, where the locking elements are retracted in the housing, and a second position where the locking elements can engage a strike plate. There is a main disadvantage to this lock. The main components, such as gear wheel, rack elements and housing are relatively difficult to manufacture and, therefore, costly. Another disadvantage is believed to reside in the oversized components, apparently to withstand high tensions usually not present in this type of lock. Also the anti slam system employed by the lock does not allow the hooks to be pushed back into the lock in case of the door being slammed while the hooks are deployed. U.S. Pat. No. 5,820,170, dated Oct. 13, 1998 and granted to Clancy for a xe2x80x9cMulti-Point Sliding Door Latchxe2x80x9d describes a mortise lock. The latter includes an actuator assembly with upper and lower actuators, a gang link, an upper link and a lower link. In its latch design, Clancy""s structure has a number of shortcomings. First, the door latch is not compact. Second, use is made of two actuators, each accomplishing the same function. Third, some components, such as the actuators, are complicated and necessitate, comparatively, more expansive technological operations. Lastly, the lock does not employ any form of anti slam mechanism.
There is accordingly a need for a mortise lock, which overcomes the disadvantages of the prior art. It is the primary objective of the present invention to provide a well-engineered mortise lock that is simple, inexpensive and easily adaptable to existing doors. It is another objective of the present invention to provide a reliable lock that comprises components that generally wear evenly.
It is yet another objective of the present invention to develop a mortise lock that is provided with an efficient anti-slam device, so that no damage can occur when the door, with the hooking assemblies in a protruded state, is slammed shut. Broadly stated, the mortise lock, according to the present invention, is directed to an elongated flat housing assembly, which encases the following components:
a pair of upper and lower hook assemblies, vertically spaced and mounted for simultaneous counter-rotational movements between an unlatched position with upper and lower hook assemblies retracted within the elongated flat housing assembly and a latched position with the upper and lower hook assemblies extending outwardly from the elongated flat housing assembly
a pair of upper and lower adjusting assemblies, vertically spaced and generally located in parallel with the pair of upper and lower hook assemblies and used for conveniently positioning the latter within elongated flat housing assembly
an actuating assembly including:
a double-armed pivot having a cylindrical body and a pair of opposed extending arms, disposed between the pair of upper and lower hook assemblies and adapted to be operated by a handle or alike
a pair of upper and lower connecting links, mounted between the double-armed pivot and the pair of upper and lower hook assemblies.
Upper and lower connection links have different configurations, each being shaped to accommodate the cylindrical body of the double-armed pivot in all the positions of the upper and lower hook assemblies, especially in the retracted position of the latter. Specifically, the upper connecting link is characterized by a first compound curvilinear configuration, so as to partially wrap around, with a sliding contact, the cylindrical body of the double-armed pivot. Conversely, the lower connecting link is characterized by a second compound curvilinear configuration, so as to partially wrap around, with a sliding contact, the cylindrical body of the double-armed pivot.